In coal and other kinds of mining by the longwall technique, it is conventional for minerals to be removed by a single or double ended ranging shearer drum, which traverses the mineral face with a rotary cutting head carried by the, or each, ranging arm to follow the seam. Typically, each drum is provided with 50 or more cutting tools but it is possible for there to be fewer than 50 cutting tools. Holders are welded to the drum to support replaceable picks designed to engage the ground. In some constructions, each holder may contain a water spray for spraying the working end (i.e., the head) of the pick and the coal with water. In general, each pick comprises a pick shank, a securement mechanism to maintain the pick in the holder, a head, and a transition area between the head and the shank.
In use, the shearer drum is rotated about its central axis. As the drum rotates, the holders move about the axis with the drum so that the picks engage the ground. The water spray, if provided, sprays water on the pick and the coal to minimize dust and the risk of frictional ignitions.
When the pick contacts the wall while the shearer drum rotates, the picks experience forces as the pick breaks up the material to be excavated. Eventually the forces cause the pick to wear out or break. As the picks wear out or break they must be replaced. A pick is often replaced several times before the holder has been worn to a point that it too must be replaced.
Generally, when the pick needs to be replaced it must be pried or otherwise forced out of the holder. Picks are generally provided with a pry finger or other notch or a recess that can be engaged with a tool to pry the pick out of the holder. The pry tool generally bears against the holder as the tool pries the pick out of the holder. However, in some cases, the finger, notch, or recess does not provide sufficient leverage to remove the pick from the holder with relatively little force. When this occurs the operator must determine how to best remove the pick from the holder. Deviating from the standard process for removing the pick from the holder may increase the amount of downtime required for replacing the picks which in turn leads to a decrease in productivity. The operator may exert a large amount of force to remove the pick from the holder, but such action may cause the operator to be injured during the removal process. In an effort to remove the pick from the holder, the operator may use the tool to engage other surfaces on the pick or holder that are not designed as removal features. Engaging the pick or the holder in areas that are not designed for engagement with a removal tool also increases the likelihood that the operator may be injured (e.g., removal tool slippage) and/or that the holder may be damaged and need to be prematurely replaced. Damaged holders must be cut from the drum and new holders welded in their place. Because of the risk of frictional ignitions and tight dark working areas, typically, shearer drums are removed from service and moved to a safe location for refurbishment, for example to the surface. Moving the shearer drum, cutting the welds between the shearer drums and the holder, and welding new holders in place is time consuming. Such refurbishment can be lengthy and expensive. There is a need for a pick and holder assembly that can be easily and quickly separated when the pick needs replacement.